U.S. Pat. No. 5,669,845 discloses a feedback control method of a speed ratio of a continuously variable transmission such as a V-belt continuously variable transmission or toroidal continuously variable transmission of a vehicle.
Under this control, a controller calculates a final target speed ratio which is a final target value of a speed ratio, based on vehicle running conditions. In order to attain the final target speed ratio with a predetermined response speed, it calculates a transient target speed ratio as a target value for every control cycle. Based on the deviation of a real speed ratio from the latest transient target speed ratio, the controller performs feedback correction of the transient target speed ratio for this cycle, and controls the continuously variable transmission by a speed ratio command value corresponding to the corrected transient target speed ratio.